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PubMed1969

Fatty acids in the lipids of marine and terrestrial nitrifying bacteria.

Fatty acids in the lipids of 19 marine and terrestrial nitrifying bacteria have been analyzed. Ammonia-oxidizing bacteria have a very simple acid composition; palmitic and palmitoleic acid account for 96 to 100% of the total acids. The fatty acids of nitrite-oxidizing bacteria cover a wider range, from C(14) to C(19), but from two to four acids still account for more than 80% of the total acids. Branched iso- and anteiso-acids are present in traces only in 2 of the 19 bacteria. The chemical and morphological similarity between blue-green algae and these bacteria is discussed.

Ammonia↗
PubMed2001

Ammonia-oxidizing bacteria: a model for molecular microbial ecology.

The eutrophication of many ecosystems in recent decades has led to an increased interest in the ecology of nitrogen transformation. Chemolitho-autotrophic ammonia-oxidizing bacteria are responsible for the rate-limiting step of nitrification in a wide variety of environments, making them important in the global cycling of nitrogen. These organisms are unique in their ability to use the conversion of ammonia to nitrite as their sole energy source. Because of the importance of this functional group of bacteria, understanding of their ecology and physiology has become a subject of intense research over recent years. The monophyletic nature of these bacteria in terrestrial environments has facilitated molecular biological approaches in studying their ecology, and progress in this field has been rapid. The ammonia-oxidizing bacteria of the beta-subclass Proteobacteria have become somewhat of a model system within molecular microbial ecology, and this chapter reviews recent progress in our knowledge of their distribution, diversity, and ecology.

Ammonia↗
PubMed2001

Potential nitrification rate as a tool for screening toxicity in metal-contaminated soils.

A potential nitrification rate test (PNR) was used to identify metal toxicity in field-contaminated soils. The test was applied to metal salt-spiked soils, to 27 uncontaminated soils, and to 15 soils that are contaminated by former metal smelting activities. Four agricultural soils (pH 4.5-6.6) were spiked with various rates of CdCl2 (0-200 mg Cd/kg dry wt) or ZnCl2 (0-3,000 mg Cd/kg dry wt) and were equilibrated more than nine months prior to testing. The soil Zn EC50s of the PNR were between 150 and 350 mg Zn/kg dry weight. No continuous decrease of the nitrification with increasing Cd application was observed. The nitrification rate was reduced by between 50 and 80% at the highest Cd application in all soils. The PNRs of 27 uncontaminated soils varied widely (0-21 mg N/kg/d), but most of this variability is explained by soil pH (R2 = 0.77). The PNRs of the 15 contaminated soils were 0 to 44% of the values predicted for an uncontaminated soil at corresponding pH. Significant toxicity in field-contaminated soils was identified if the PNR was outside the 95% prediction interval of the PNR for an uncontaminated soil at corresponding pH and was found in seven soils. These soils contain 160 to 34,000 mg Zn/kg dry weight and 5 to 104 mg Cd/kg dry weight and had a pH >5.7. No toxicity could be detected below pH 5.6, where even a zero PNR value is within the 95% prediction interval of uncontaminated soils. It is concluded that the nitrification is sensitive to metal stress but that its power as a soil bioassay is low because of the high variability of the endpoint between uncontaminated soils. The ecological significance of the assay is discussed.

Environmental Monitoring↗
PubMed2006

Biosensor-based control of nitrification inhibitor in municipal wastewater treatment plants.

The effect of potassium cyanide (KCN) on nitrification processes in municipal wastewater treatment plants was studied by batch nitrification tests, which indicated that nitrification processes tend to be inhibited at a lower KCN concentration than the present discharge standard to sewerage. The experiment of the biosensor using nitrifying bacteria was also conducted for continuous monitoring of nitrification inhibitor in influent wastewater, and demonstrated that the biosensor can detect KCN at as low as EC10 of the abovementioned batch nitrification test. Moreover, to determine the effectiveness of application of the biosensor to avoid the impact of KCN due to an accidental spillage in a sewerage system, KCN was intentionally injected into the experimental models of activated sludge process equipped both with and without the biosensor. The model with the biosensor that could detect KCN could divert the wastewater including KCN to a refuge tank, which resulted in the avoidance of upset of the activated sludge process. On the other hand, the model without the biosensor was upset in the nitrification process due to KCN. Such differences demonstrate the effectiveness of the biosensor applied to countermeasures of an accidental spillage of toxic chemicals to avoid upset of nitrification in municipal wastewater treatment plants.

Bioreactors↗
PubMed1999

VFEU water quality control in STS-95 mission.

In STS-95 Space Shuttle mission, an aquatic animal research facility, Vestibular Function Experiment Unit (VFEU), was flown to perform neurobiological experiment with marine fish, oyster toadfish. For this purpose, we have developed a sea water purification system using highly active nitrifying bacteria at low temperature. With this system, the water quality in the VFEU was maintained in sufficient condition to keep the toadfish in healthy state for 9 days of the mission. This report summarizes the efficiency of the filter system based on the results from pre-flight bacterial preparation, water analysis of samples taken during flight, and the post-flight analysis of the bacterial filter.

Ammonia↗
PubMed1999

Closed water recirculating system for fish rearing equipped with bioreactor capable of simultaneous nitrification and denitrification.

Five crucian carp, Carassius auratus langsdorfiicarps had been reared in a closed water recirculating system. The system was equipped with the compact bioreactor using the plate gels capable of both nitrification and denitrification in a single unit. Ammonia and nitrite concentrations in the rearing water had been maintained below 0.05 mg-N/L, and nitrate concentration also controlled between 2 and 8 mg-N/L with the bioreactor. As concerns nitrogen budget in the closed system, 95.0% of nitrogen income from feed was lost as nitrogen gas from the closed system. All fish was alive for 91 days without any unusual behavior. Thus, the bioreactor performed both nitrification and denitrification abilities enough to rear the five fish for 91 days. The bioreactor using the plate gels would be effective to simplify the closed system both physically and operationally, since it can remove the ammonia excreted from fish as nitrogen gas by a single step.

Ammonia↗
PubMed1999

R&D of long-term life support system by using electrochemically activated biofilm reactor of aquatic animals for space examinations.

We have developed the long-term life support system that enables the experiment of aquatic animals breeding for 90 days or more for the future experiments in orbit. In order to enable long-term breeding of wide aquatic animals, it is necessary to remove nitrate produced by biological nitrification. Then, we examined a denitrification method to use an electrochemical reaction of biofilm-electrode reactor. In this research, we have not kept the aquatic animals actually but imitated breeding of five goldfish. The ammonia of about 250 ppm was added in breeding water through 90 days. As a result, neither ammonia nor nitrite accumulated 0.1 ppm and nitrate could be suppressed to about 10 ppm.

Ammonia↗
PubMed1993

Simultaneous nitrification and denitrification using immobilized microorganisms.

Nitrogen removal from wastewaters is a multiple step process in which nitrification is often a problem due to the slow growth rates of the nitrifying bacteria. By immobilization of these bacteria, nitrification can be efficiently accomplished in compact reactors. In this paper, the possibilities of integrated nitrification and denitrification within a single reactor system are evaluated. Two main systems are studied: a) Nitrosamines europaea and Pseudomonas denitrificans co-immobilized in a a gel bead and operated in an air-lift reactor; b) the same bacteria separately immobilized and operated in different compartments of a multiple gas-lift reactor.

Ammonia↗
PubMed2002

Intestinal urea metabolism: could the bacteria involved in nitrogen cycle lead to reutilization of intestinal urea nitrogen in uremic rabbits?

We aimed to evaluate the effect of bacteria involved in the nitrogen cycle on the reutilization of intestinal urea nitrogen in uremic rabbits. New Zealand white rabbits were made uremic via bilateral nephrectomy. Study and control rabbits were given live and heat-inactivated bacteria through their jejunostomies. After they were injected with 99mTc biurea intravenously, serial serum and stool levels of labeled nitrogen were assessed by instant thin-layer chromatography, and the change in the labeled-nitrogen level was determined. The serum labeled-nitrogen level increased significantly in the study group (r=0.990); however, this level decreased in the control group (r=0.662). Furthermore, the labeled-nitrogen level in the stool samples increased throughout the study in the control rabbits, but it decreased after the 6th hour in the study group. In conclusion, the results of this study suggest that when the bacterial flora of the intestinal system is changed to include bacteria involved in the nitrogen cycle in uremic rabbits, the intraintestinal and systemic nitrogen metabolisms could both be altered in favor of positive nitrogen balance.

Animals↗